This invention relates to multiple speed winches having two separate and selectively shift sequences.
Conventional multiple speed winches comprise a rotatable drum mounted on a base support and a central driven shaft connected by a gear train to an inner ring gear surface on the drum. These winches have mechanisms to enable driving of the drum in a clockwise direction at progressively higher gear ratios upon reversal of rotation of the drive shaft.
Four speed winches are typically employed on large sailboats for the purpose of providing different gear ranges depending on whether the boat is sailing upwind or downwind. In the former, the winch is employed to pull in the sheet of a genoa, and in the latter, the sheet of a spinnaker is wrapped around the drum of the winch. Since the boat may frequently tack when beating upwind, it is desirable to have a first gear of a high ratio, e.g., 1:1 to enable slack line to be trimmed in rapidly. As tension increases, third and fourth gears can be selected automatically by successive reversals of rotational direction of the drive shaft.
When sailing downwind, a first gear ratio of 1:1 does not provide sufficient mechanical advantage, since the sheet is under constant tension. Thus, a second gear is provided which has a gear ratio between the first and third gears. Also, means are provided to allow operation of the winch between second and third gears upon driving the drive shaft in opposite rotational directions.
U.S. Pat. No. 4,725,043 describes a four speed winch, which is in effect, a conventional three speed winch with a manually selectable second speed added to the main drive train. In first speed, the drum and shaft are driven together by a one way ratchet mechanism, by rotating the shaft in a clockwise direction. When rotation of the shaft is reversed, first speed is disengaged by a spring mechanism connected to an external central button. Upon rotation of the shaft successively in the counterclockwise and clockwise directions, third and fourth speeds are engaged. First speed may be again selected by depression of the central button.
Second speed is also manually engaged via a lever and operates through the final drive gears of the winch. While such arrangement operates successfully, it is inefficient because the relatively high second gear must drive through a long drive train through the final drive. Also, since second gear operates through the main drive train, the winch will automatically shift from second to third and then to fourth unless a separate mechanism is used to lock out fourth gear.